The present invention relates to a whipstock of the type commonly used for setting in a casing, cutting a window in the casing, drilling a lateral from the casing into a formation, and/or diverting a downhole tool into a lateral extending from the casing. More particularly, this invention relates to a combination whipstock and anchor tool which may be run in a well at a relatively low cost and reliably set in the well for achieving its diverting function.
A whipstock is a downhole diversion tool inserted into a wellbore and used to deflect a drill bit or other tool in a direction that is angularly offset with respect to the orientation of the original wellbore. The deflected mill may thus establish a new or additional drilling path, commonly referred to as a lateral. A whipstock may also divert a slotted liner or other tubular that is run into the drilled lateral. A whipstock positioned in a casing string on an anchor thus provides an angled whipstock diversion face at a desired depth in the wellbore in order to conduct various side tracking or lateral drilling operations through the casing string.
Many whipstocks are run in a well and are set on an anchor which was previously run in the well and fixed into biting engagement with the casing. Downhole anchors are thus conventionally used for supporting a whipstock within a casing string, and in many applications the whipstock may be retrieved to the surface with the anchor left in place. Various types of anchors are thus available for this purpose. A mechanically set anchor for supporting a whipstock in a well is disclosed in U.S. Pat. No. 5,193,620. U.S. Pat. No. 5,335,737 discloses a hydraulically set anchor. Thru tubing anchors for supporting a whipstock are disclosed in U.S. Pat. Nos. 5,595,247 and 5,678,635.
One of the advantages of providing an anchor separate from the whipstock is that a properly set anchor provides a reference point so that the face of the whipstock may be properly oriented to achieve a desired azimuthal direction for the diversion operation. A whipstock may thus be retrieved to the surface and reoriented so that, when later reinserted in the well, the whipstock face will be at a known azimuth relative to the set anchor. An anchor which may be fixed within a well and a whipstock oriented at a desired azimuth relative to the anchor is disclosed in U.S. Pat. No. 5,467,819.
One of the disadvantages with a system which provides an anchor separate from the whipstock is that one trip is generally required to position and set the anchor downhole, then another trip is subsequently used to set the whipstock in the hole on the anchor. A combination whipstock and anchor for setting in a well in one trip is disclosed in U.S. Pat. No. 3,115,935. U.S. Pat. No. 5,154,231 also discloses a combination whipstock and a hydraulically set anchor. A combination anchor and whipstock have been sold by TIW Corporation as the SS-WS Whipstock Packer with Anchor. U.S. Pat. No. 5,222,554 discloses a combination whipstock and anchor, with the anchors consisting of axially spaced pivot members which swing out from the whipstock body. U.S. Pat. No. 5,494,111 discloses a permanent whipstock and anchor tool which similarly uses pivoting anchor members.
A significant problem with the combination whipstock and anchor assemblies known in the prior art is cost of these tools, and/or problems associated with reliably setting the tools in the casing. The anchor components of many of these prior art tools are quite complex and expensive. Other tools, such as those using anchor members which pivot with respect to the whipstock body, do not provide reliable engagement with the casing. If the operator cannot rely on the anchor remaining in place when the mill or other tool engages the anchor, the whipstock will not be widely accepted in the industry.
The disadvantages of the prior art are overcome by the present invention, and an improved whipstock and anchor are hereinafter disclosed. The combination whipstock and anchor of the present invention may be provided at a relatively low cost, yet may be reliably set in a casing and remain in the set position during the various diversion operations. In one embodiment, the combination whipstock and anchor is retrievable to the surface. The whipstock and anchor may also be used in thru tubing operations.
A combination whipstock and anchor assembly includes a whipstock body having a whipstock diversion face, at least one wedge member movable relative to the whipstock body, and an actuation member for moving the at least one wedge member from a run in position to a set position. The whipstock body includes a lower wedge engaging surface, and a wedge member has a whipstock body engaging surface in sliding engagement with the wedge engaging surface. The wedge member may support one or more wedge slips for anchored engagement with the casing. The combination whipstock and anchor assembly may be used in conventional or thru tubing operations, and if desired the whipstock may be retrieved to the surface after the setting operation.
In a preferred embodiment, the actuation member includes an elongate rod moveable within a thru bore provided in the whipstock body. A hydraulic actuator may be positioned above the whipstock body for moving the elongate rod from the run in to the set position. The rod may be provided with a shear member to shear after the wedge member has been moved to the set position.
In one embodiment, two axially spaced slips are provided on the wedge member. The circumferentially opposing surface of the whipstock body engages the casing in one embodiment, while in another embodiment at least one slip provided on the whipstock body engaging the casing. The wedge engaging surface and the whipstock body engaging surface may be provided with a dovetail interconnection. A counterbalance may be provided for positioning the whipstock body in the well prior to setting the whipstock assembly.
A ratchet mechanism may be positioned within the thru bore of the whipstock body below the shear member for retaining the whipstock body and a wedge member in the set position. In one embodiment, the back surface whipstock body circumferentially opposite the whipstock diversion surface is spaced from the casing so that the whipstock is effectively xe2x80x9ctiltedxe2x80x9d within the casing when in the set position. In the latter embodiment, the whipstock diversion face may have a substantially uniform depth cut in the whipstock body.
A plurality of wedge members may be provided, with one of the wedge members engaging the lower wedge engaging surface on the whipstock body. Each of the wedge members is slidably movable relative to the whipstock body and to another of the wedge members.
The elongate rod may include a bushing slidable within the thru bore. A lower rod portion may be pivotally interconnected with the bushing and the lower wedge member.
An upper portion of whipstock body may include a whipstock retrieval surface for engaging a retrieval tool to retrieve the whipstock and anchor assembly to the surface.
According to the method of the present invention, the whipstock body and the at least one wedge member having a wedge slip supported thereon are run into a well and into the interior of a downhole casing. Thereafter the elongate rod is moved relative to the whipstock body from a run in position to a set position, thereby moving the at least one wedge member to the set position.
The whipstock body and the at least one wedge member in the run in position may be passed through a tubing or other restriction in a casing, and thereafter set within that casing or another casing at a location below the restriction. An actuator may be positioned above the whipstock member, and a shear member may be provided in the elongate rod. The actuator may be activated to shear the shear member after moving the elongate rod to the set position, and thereafter the actuator may be retrieved to the surface. A retrieval surface may be provided on the whipstock body for engagement with a retrieval tool while in a set position.
It is an object of the present invention to provide an improved whipstock and anchor assembly and an improved method for setting a whipstock and anchor assembly in a casing. If desired, the assembly and the method of the present invention may be used in thru tubing operations wherein the tubing O. D. is less than the I.D. of the casing. The whipstock and anchor assembly may also be retrieved to a surface through the tubing after being set in a well.
It is a related object of this invention to improve the reliability of setting a relatively low-cost whipstock assembly in a casing. An elongate rod may be provided for moving the wedge member from the run in position to the set position. The whipstock body, the wedge member, and the rod may be lowered into a well, then the elongate rod moved from a run in position to a set position, thereby moving the wedge member to the set position.
A significant feature of the present invention is that the whipstock and anchor assembly provides an effective and reliable mechanism for effectively securing the position of a whipstock body in the casing. The whipstock and anchor assembly may be provided at a relatively low cost, thereby facilitating the economical recovery of hydrocarbons.
An advantage of the present invention is that the whipstock and anchor assembly may include a ratchet mechanism which ensures that the assembly remains in the set position until it is intentionally disabled.
Another advantage of this invention is the reliability of the whipstock setting operation, which is enhanced by utilizing an elongate rod to move the whipstock assembly components to a set position.
These and further objects, features and advantages of the present invention will become apparent from the following detailed description, wherein references is made to the figures in the accompanying drawings.